// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.

#include "util/logging.h"

#include <errno.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <limits>
#include "leveldb/env.h"
#include "leveldb/slice.h"

namespace leveldb {

    void AppendNumberTo(std::string *str, uint64_t num) {
        char buf[30];
        snprintf(buf, sizeof(buf), "%llu", (unsigned long long) num);
        str->append(buf);
    }

    void AppendEscapedStringTo(std::string *str, const Slice &value) {
        for (size_t i = 0; i < value.size(); i++) {
            char c = value[i];
            if (c >= ' ' && c <= '~') {
                str->push_back(c);
            } else {
                char buf[10];
                snprintf(buf, sizeof(buf), "\\x%02x",
                         static_cast<unsigned int>(c) & 0xff);
                str->append(buf);
            }
        }
    }

    std::string NumberToString(uint64_t num) {
        std::string r;
        AppendNumberTo(&r, num);
        return r;
    }

    std::string EscapeString(const Slice &value) {
        std::string r;
        AppendEscapedStringTo(&r, value);
        return r;
    }

    bool ConsumeDecimalNumber(Slice *in, uint64_t *val) {
        // Constants that will be optimized away.
        constexpr const uint64_t kMaxUint64 = std::numeric_limits<uint64_t>::max();
        constexpr const char kLastDigitOfMaxUint64 =
                '0' + static_cast<char>(kMaxUint64 % 10);

        uint64_t value = 0;

        // reinterpret_cast-ing from char* to unsigned char* to avoid signedness.
        const unsigned char *start =
                reinterpret_cast<const unsigned char *>(in->data());

        const unsigned char *end = start + in->size();
        const unsigned char *current = start;
        for (; current != end; ++current) {
            const unsigned char ch = *current;
            if (ch < '0' || ch > '9')
                break;

            // Overflow check.
            // kMaxUint64 / 10 is also constant and will be optimized away.
            if (value > kMaxUint64 / 10 ||
                (value == kMaxUint64 / 10 && ch > kLastDigitOfMaxUint64)) {
                return false;
            }

            value = (value * 10) + (ch - '0');
        }

        *val = value;
        const size_t digits_consumed = current - start;
        in->remove_prefix(digits_consumed);
        return digits_consumed != 0;
    }

}  // namespace leveldb
